1. Field of the Invention
The present invention relates to a vehicle burglar alarm system and more particularly, to a vehicle burglar alarm system with GPS (Global Position System) recognition, which controls the operation of the alarm subject to the satellite signal receiving status of the GPS.
2. Description of Related Art
In order to prevent stealing of the vehicle by a thief or the occurrence of abnormal conditions, the vehicle owner will equipped the vehicle with a vehicle alarm system. After leaving from the vehicle, the vehicle owner can initiate the burglar alarm mode of the vehicle burglar alarm system, driving different sensors to detect different locations at the vehicle.
When an abnormal vehicle condition is encountered, for example, an intruder enters the vehicle, the respective sensor is induced to trigger the alarm of the vehicle burglar alarm system. A vehicle burglar alarm system generally uses a siren for producing a sharp sound to call people's attention and to frighten the thief into running away, or to have the vehicle owner come back to the parking side of the vehicle to check the abnormality when heard the sharp sound of the siren.
The sharp sound of a siren can frighten the thief into running away, however it is hearable within a limited distance. The vehicle owner may be not able to hear the sharp sound of the siren when the vehicle burglar alarm system of his (her) vehicle is triggered, thereby missing the chance of saving the vehicle. Further, if a tow truck is towing the vehicle and the siren of the vehicle burglar alarm system keeps making a loud sharp sound, the owner of the vehicle may not find this status. In this case, the owner of the vehicle cannot trace the vehicle, and the owner of the vehicle knows that the vehicle has been towed to another place by a tow truck only when returned to the parking side. These conditions occur just because the vehicle burglar alarm system does not provide the function of actively informing the owner of the vehicle of the occurrence of an abnormality. Further, the noise of the loud sharp sound of the siren of a vehicle burglar alarm system is not friendly to the surroundings.
In recent years, a car may be equipped with a GPS (Global Position System) for navigation. As shown in FIG. 1, when a vehicle is at a local area 200 without shelter and the GPS of the vehicle is started, the GPS receive satellite signal from a group of satellites 101˜108 through the many channels thereof. After initiation, the GPS receives time signal from the satellites 101˜108. Thereafter, the satellites 101˜108 are classified into sets each including three satellites, and then the set of satellites having the least HDOP (Horizontal Dilution of Precision) value is selected for computing the location of the GPS. For example, satellites 101, 102 and 108 are the same set, and the signals of the satellites 101, 102 and 108 are used for the computation of the location of the GPS if the HDOP value of the set of satellites 101, 102 and 108 is the least.
If the satellite signal of the satellite 108 is blocked and not receivable, the satellite signals from the satellites of another set having the second least HDOP value are used for the computation of the location of the GPS. However, when the car entered a tunnel, parking tower, or sheltered place, the GPS receives no satellite signal, and it takes about 10˜30 minutes to reboost the GPS. The use of a GPS in a vehicle burglar alarm system in accordance with conventional techniques may encounter cannot effectively prohibit a thief from stealing the car when the car is parking at a parking tower or sheltered place. Because reboosting the GPS takes about 10˜30 minutes, the car owner may know the location of the car after the car has been moved by the thief to a place far away from the parking place. If the thief put the car in a cargo container before completion of reboosting of the GPS, the GPS cannot compute the location.
Therefore, it is desirable to provide a vehicle burglar alarm system with GPS recognition that eliminates the aforesaid problem.